Retinoblastoma Genetics

If there is more than one retinoblastoma, affecting one or both eyes and/or if any other relatives have had this disease, the chances of germline disease are 100%.

When there is only one retinoblastoma in only one eye, and when no other family members have had this disease, the chances of germline disease are approximately 12% (i.e., ‘one-in-eight’).

The first step is therefore to list all the relatives and find out whether any have had retinoblastoma and, if so, who has had the disease.

The next step is to examine the parents as well as any brothers and sisters for retinal tumors and tumors in other parts of the body. Some retinoblastomas die or stop growing without ever causing any symptoms (i.e., retinoctyomas or retinomas).

Genetic tests can be performed to determine whether a retinoblastoma mutation is present and to identify the gene that is mutated. There are many genes that can result in retinoblastoma if mutated.

If the eye is removed, a sample can be obtained from the tumor itself. If the eye is not removed, a blood sample or a buccal scraping (from the inside of the mouth) can be taken.

Each family with germline retinoblastoma has a mutation that is particular to that family. In other words, different families have different mutations. Once the mutation particular to an individual patient is identified, it becomes easier to test brothers, sisters and other relatives for the same mutation. This makes it possible to identify which relatives are at risk of retinoblastoma so that they can receive special examinations to detect and treat any tumors as early as possible.

Genetic tests and genetic counseling are provided by the geneticist, who has special expertise in this aspect of care.